id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
4649	token_functions.hpp (220) :  fix for warning C4127 conditional expression is constant	Andrew Macgregor <aamacgregor@…>	jsiek	"MSVC gives a compiler warning for the following piece of code (starting at line 220) in token_functions.hpp:

----------
 if (sizeof(char_type) == 1)
   return std::isspace(c) != 0;
 else
   return std::iswspace(c) != 0;
----------

The warning is obvious:
  warning C4127: conditional expression is constant

The warning is causing automated project builds to fail when 'fail on warning' and /W4 (maximum warnings) are set.

Please can you make the run-time check for sizeof(char_type)==1 into a compile-time check? A solution could be to change:

----------
 if (sizeof(char_type) == 1)
   return std::isspace(c) != 0;
 else
   return std::iswspace(c) != 0;
----------

for something along the lines of

----------
 return check_isspace<traits, sizeof(char_type)>::value_for(c);
----------

where check_isspace is defined as follows:
----------
 template <typename traits, size_t char_type_size>
 struct check_isspace
 {
   typedef typename traits::char_type char_type;

   static bool value_for(char_type c) { return std::iswspace(c)!=0; }
 };

 template <typename traits>
 struct check_isspace<traits, 1>
 {
   typedef typename traits::char_type char_type;

   static bool value_for(char_type c) { return std::isspace(c)!=0; }
 };
----------
"	Bugs	closed	To Be Determined	tokenizer	Boost 1.44.0	Problem	fixed	isspace